Fluctuation conductivity and microscopic granularity in bi-based high-temperature superconductors

• Autor(a) principal: Jurelo, Alcione Roberto
• Data de Publicação: 1997
• Outros Autores: Kunzler, Julio Vitor, Schaf, Jacob, Pureur Neto, Paulo, Rosenblatt, Jorge
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRGS
• Texto Completo: http://hdl.handle.net/10183/104157
• topic: Física da matéria condensada; Supercondutores; Supercondutividade

Systematic conductivity measurements near Tc in granular (Bi,Pb)-Sr-Ca-Cu-O superconductors are presented, and focus is given on the interplay between thermal fluctuations and disorder at micro- and mesoscopic levels. Experiments show that the resistive transition is a two-step process. In the normal phase, Gaussian and critical fluctuation conductivity regimes were identified. Both are affected by local disorder. Particularly, the critical regime is characterized by a power law with exponent λcr~3, which we interpret as resulting from microscopic granularity. Below Tc and in the regime describing the approach to the zero-resistance state, fluctuation conductivity diverges as expected in a paracoherent-coherent transition of a mesoscopic granular superconductor. The results show that, instead of trivially rounding the transition, disorder at micro- and mesoscopic levels preserves a true critical phenomenology in granular superconductors.